The general goal is to continue our successful cooperative efforts to develop new instruments and assessment methods for evaluating clinical effectiveness in AD clinical trials. This work is accomplished by capitalizing on the unique collective expertise, experience, and patient resource of the ADCS through subcommittees of ADCS experts that develop new or improved measures and evaluation methods and facilitate the use of these methods in ADCS clinical trials. The ADCS Instrument Committee (consisting of the Project Director, the chair of each subcommittee and the ADCS Statistician) will continue to be responsible for coordinating and integrating the work of the subcommittees, for evaluating the utility of new measures by incorporating them into multi- site clinical trials, and for working closely with ADCS investigators in selecting outcome measures for ADCS clinical trials. Improved evaluation of treatment efficacy is necessary to optimize determination of whether a drug has a therapeutic effect, whether the effect observed is clinically meaningful and of sufficient magnitude to outweigh possible risks, and ultimately, whether the treatment has a favorable socioeconomic impact. Over the past 10 years, the ADCS Instrument the ADCS Instrument Committee has helped to define the state of the art in assessment for AD and MCI clinical trials. However, further work is now needed to improve the efficiency and reduce the cost of measures used in AD primary prevention trials. Since there are now promising treatments that may slow the disease progression or prevent AD, the current project will focus on developing sensitive and more efficient and more efficient methods for evaluating change in normal elderly subjects. The specific aims of the Prevention Instrument Protocol are: (1) to assess the reliability, efficiency, validity and sensitivity to longitudinal change and early AD or new instruments in each of five domains. These instruments are mostly self-administered and designed for use in AD prevention. 650 non-demented elderly subjects participating in the ADCS Primary Prevention Trial will also participate in this Prevention Instrument Protocol. The 5 domains are global change, cognition, activities of daily living, quality of life and pharmacoeconomics; (2) to evaluate and compare two self-assessment methods of data acquisition: (a) In-clinic, and (2) at-home, by mail, with assistance via telephone. 699 subjects will be randomized to complete the instruments annually, 300 at their clinic visits for the Primary Prevention Trial and 300 at home, and (3) to conduct a pilot evaluation of the feasibility and unity of web-based data acquisition of the new assessments. 50 additional subjects who have access to a computer and the Internet will participate in this pilot study.